S ree Pee Fi nae bi — ow 
Ge ie i ai, 
as Infusoria flagellata. 193 
demonstrated in two ways at least. In the first place, it is 
highly flexible and retractile, as it occasionally shows itself to 
be, either by narrowing its aperture almost to absolute closure 
(fig. 24, b), or by reducing its height to a small fraction of its 
greatest altitude (as seen in fig. 27, 6), and then extending it- 
self again, within a few seconds, by a direct protrusion (fig. 26,6), 
to its original proportions (fig. 25,6). In the second place, it 
divides longitudinally, like the rest of the body, when self- 
division occurs (figs. 11-22)—-a process in which no genuine 
calycle was ever known to be concerned. In an adult state 
(figs. 8, 11, 244, 25) it is slightly constricted by a gradual in- 
curvature extending from the base (fig. 244, 0?) to the distal 
margin (61); but frequently, and apparently always just before 
self-division takes place, its sides bulge slightly outward (fig. 
11,6). ‘Taking all these things into consideration, therefore, 
it is perfectly clear that this infusorian is not a calyculate form, 
but one of those mimetic shapes which occasionally deceive 
the eye and puzzle the observer, until he becomes familiar with 
their various phases of growth and development. 
This phenomenon is most singularly exemplified by the 
creature before us now, in its almost indistinguishable resem- 
blance to a genuine calyculate Flagellifer (Salpingeca marina, 
Pl. VI. figs. 28-32) which abounds in our marine waters. 
This similarity arises chiefly from the fact that the urceolus 
(figs. 28-32, c) of the latter has an oval shape like the body 
of the former, and is constricted so—closely at its aperture (c!) 
as to present the appearance of being continuous with the high » 
campanuliform collar (6) which projects from the front. Usu- 
ally, however, the body proper of this animal (Salpingeca 
marina, nov. sp.) lies loosely within, and considerably with- 
drawn (fig. 28) from, the parietes of its calyx ; but occasionally 
in older specimens it completely fills (fig. 81) its sheath; and 
then it is next to impossible to distinguish it, in this respect, 
from a Codosiga. In a sessile freshwater species of Salpin- 
_geca of the urceolate type (S. amphoridium, figs. 37-37°), 
the resemblance to Codosiga is almost as strong, but the dif 
ference is equaliy marked. 
The flagellum (figs. 8 &e., ff) is the only prehensile organ 
which Codosiga possesses. It arises from the middle of the 
low truncate cone (7) which constitutes the front, and ‘con- 
sequently within the campanulate collar (6), reminding one of 
the curvate style of a labiate monopetalous flower. It is usu- 
ally rigid, excepting at the tip, which is constantly occupied 
in throwing particles of various kinds toward the mouth (m) 
by vigorous spasmodic incurvations or jerks. At its basal half 
it is slightly curved towards the longer side of the body, but 
